1. Field of the Invention
The present invention relates to a method of obtaining a free disperse system and device which will make it possible to produce a controlled hydrodynamic cavitation and to regulate the intensity parameters of a hydrodynamic cavitation field. Selection of the parameters with regard to the properties of components of the fluid under treatment which in turn will make it possible to effectively treat the components with different physico-chemical characteristics. The invention particularly relates to a cavitation device for effecting this method with a baffle body of such a construction which will allow the multiplicity of treatment to be regulated along with an increase in degree of cavitation which will substantially improve the quality of an obtained free disperse system and will substantially extend technological capabilities of the method.
2. The Prior Art
Widely known in the prior art are methods of obtaining free disperse systems and particularly lyosols, diluted suspensions and emulsions, using the effect of cavitation. These systems are fluidic and particles of a dispersed phase have no contacts, participate in a random beat motion and freely move by gravity. In these methods, the emulsification and dispersion processes are accomplished due to cavitation effects expediently set up in the flow under treatment by hydrodynamic means at the expense of a sharp change in geometry of the flow.
Also known in the prior art are devices for effecting these methods of which the basic element is presented by a baffle body installed in a flow channel in the direction of a hydrodynamic flow.
Phenomenon of the hydrodynamic cavitation resides in the formation of cavities filled with a vapor-gas mixture inside the liquid flow or at the boundary of the baffle body due to a local pressure drop caused by movement of the fluid. Mixing, emulsification and dispersion effects of the hydrodynamic cavitation result from a substantial plurality of force effects on the treated mixture of components due to the collapse of cavitation bubbles. The collapse of cavitation bubbles near the boundary of "liquid-solid particles" phases results in dispersion of these particles in the fluid and in formation of the suspension, while in the "liquid-liquid" system one fluid is atomized in the other fluid and results in formation of the emulsion. In both cases, the boundary of solid phases is destroyed, i.e. eroded and a dispersive medium and a dispersed phase are formed.
For the most part, the models explaining the mechanism of emulsification and dispersion processes accomplished by means of cavitation are based at the present time on the use of a cumulative hypothesis of the cavitation effect on a surface to be destroyed. The process of dispersion by means of cavitation is associated with the formation of cumulative microjets. It is supposed, that due to the interaction of a shock wave set up by the collapse of cavitation bubbles with the bubbles arranged at the boundary of the phases, the cumulative microjets are formed. Intensive mixing and dispersion is explained by the formation of high-intensity microvortices and by a sequential disintegration of the cumulative microjets. The process of the fluid atomization is caused by tangential stresses acting on the referred fluid and occurring at the boundaries of cavitation microvortices, while the dispersion of solid particles is accomplished due to a hydrodynamic penetration of a cumulative microjet into a particle.
In addition to erosion effects caused by the collapse of cavitation bubbles, other physico-chemical effects occur serving as additional factors in the intensification of technological processes.
It should also be noted that physical characteristics of the mixture of components in the flow under treatment have a substantial influence on the erosion activity of cavitation bubbles. For example, increase of viscosity, decrease of surface tension and density of the fluid, as well as increase of the gas content therein reduce the efficiency of the cavitation effect.
There is also known, a method of obtaining a free disperse system, i.e. a suspension of fibrous materials, involving the passage of a hydrodynamic flow of fibrous materials through a channel internally accommodating a baffle body installed across the flow for providing a local contraction of the flow and forming downstream of the referred body a hydrodynamic cavitation field acting on the flow of fibrous materials until the suspension of the referred materials is formed.
An attempt was made for effecting the method described hereinabove, in which a device was proposed consisting of a housing with inlet and outlet openings, a contractor, an internal flow channel accommodating a solid cylindrical baffle body and a diffuser (U.S. Pat. No. 3,834,982) arranged in succession on the inlet opening side and connected together.